["Archives of Insect Biochemistry and Physiology, Volume 121, Issue 4, April 2026. ", "The study detected the effects of different concentrations of flavonoid rutin exposure on FAW (F0 and F1). The results indicated that rutin suppressed the growth and development of FAW, affecting both body weight and size in a dose‐dependent manner. These findings highlight that rutin exposure disrupted the nutrition and energy metabolism of FAW, reducing FAW population growth and fitness with transgenerational effects.\n\n\n\n\n\nABSTRACT\nSpodoptera frugiperda is a highly destructive agricultural pest that poses a significant threat to crops worldwide. While traditional insecticides offer effective control, their environmental impact and potential for fostering pest resistance raise critical concerns. Present study investigates the effect of rutin, a plant‐derived flavonoid, on the ecological fitness of FAW larvae. Our bioassays demonstrate that flavonoid rutin exposure leads to a significant reduction in body weight and size in a dose‐dependent manner. Furthermore, an analysis using age‐stage, two‐sex life tables reveal detrimental effects on survival rates and an extension of developmental duration in both F0 and F1 generations, with transgenerational impacts observed. Importantly, reduced food consumption correlates with altered gene expression and enzyme activities related to sugar and lipid metabolism in the midgut of F0 larvae. These findings enhance our understanding of the ecological implications of phytochemicals like rutin on pest population dynamics, highlighting their potential as eco‐friendly alternatives for integrated pest management strategies.\n"]